1. Field of the Invention
The present invention relates generally to gas distribution plates utilized in semiconductor wafer processing equipment, and more particularly to a liquid cooled gas distribution plate for use in chemical vapor deposition chambers.
2. Brief Description of the Prior Art
Gas distribution plates are commonly utilized in chemical vapor deposition (CVD) chambers to uniformly distribute the gas upon its introduction into the chamber. Such a uniform gas distribution is necessary to achieve uniform deposition characteristics upon the surface of a wafer located within the chamber.
Problems have arisen in utilizing the currently available gas distribution plates when the temperature of the plate causes unwanted reactions between components of the deposition gas. A particular instance in which such problems have arisen concerns the deposition of tungsten silicide upon a wafer. Specifically, to deposit a layer of tungsten silicide, the two gases, tungsten hexafluoride and silane, are inletted through a manifold and mixed in a water cooled gas mixing chamber within the manifold head. The cooling is necessary because the two gases will react to form a solid, tungsten silicide, at temperatures greater than approximately 25 degrees centigrade. After mixing in the cooled manifold head, the gaseous mixture is passed through the standard gas distribution plate system, whereby a uniform distribution of the gaseous mixture is introduced into the deposition chamber. The gaseous mixture then impinges upon a warmed wafer within the chamber, whereupon the two gases react to deposit tungsten silicide upon the wafer.
Particulate contamination problems have occurred in the above described systems when the prior art gas distribution plate has warmed to temperatures greater than 25 degrees centigrade. When such plate warming occurs, the two gases react at the gas distribution plate to form large particulates which clog the gas distribution holes of the plate. Additionally, a layer of tungsten silicide may form on the inner surface of the plate to later flake off in large particulates which rain down upon the wafer to create an uneven tungsten silicide layer, whereby the wafer is contaminated and rendered valueless. The inventors are not aware of any prior art gas distribution plates that are designed to solve this problem. Of course, similar problems may exist with other gases and/or gaseous mixtures where the temperature of the gas distribution plate causes unwanted gaseous reactions.
The temperature controlled gas distribution plate of the present invention includes a liquid cooling passage, with inlet and outlet ports, that is formed within the gas distribution plate. In the preferred embodiment, the plate is formed with an upper passage cover and a lower base having a liquid passage channel formed within the side walls thereof. The cover and base are welded together to form a sealed liquid passage within the plate through which the liquid coolant flows.
It is an advantage of the present invention that the temperature of the gas distribution plate can be controlled.
It is another advantage of the present invention that gaseous reactions are inhibited from occurring at the gas distribution plate.
It is a further advantage of the present invention that particulate contamination of wafers in a CVD chamber can be minimized.
It is yet another advantage of the present invention that the clogging of holes in the gas distribution plate through the unwanted reaction of gases passing through the plate can be eliminated.
It is yet a further advantage of the present invention that it is fabricated to be engaged to a base plate that possesses substantially the same outer dimensions as existing base plates, whereby it may be retrofit into existing CVD chambers to improve the performance of such chambers.
These and other features and advantages of the present invention will no doubt become apparent to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which are illustrated in the several figures of the drawing.